1. Field of the Invention
The present invention pertains to apparatus for use in testing the fluid tightness of closed vessels or fluid systems, such as found in the pressurized cooling system of an internal combustion engine and the fluid transmission of an automobile, and more particularly, to apparatus for detecting and/or quantifying fluid leakage from a fluid system that is under pressure when in use, such as through imperfections in the housing or sealing structure of the fluid system whereby to warn the provider of such fluid system that a leakage condition exists.
2. Description of the Prior Art
The automobile is comprised of many components that take many forms and some are very complex, such as the engine and the coolant system for circulating coolant for cooling the engine cylinders. The engine is assembled from separate parts, some possibly die cast, to form a housing having various ports, internal passageways and/or inside chambers, and seals. The walls and junctions of the engine housing may have minor imperfections, and the components, when assembled, may have a gap or minor separation between mated parts, and thus have a potential for developing a leak.
In these systems, fluids are introduced into interior fluid chambers at high positive pressure. Since the fluid system operates at atmospheric pressure, if there is a hole or imperfection in the construction of the fluid system, the pressure differential will cause the fluid inside the system to be forced outside (i.e., develop a vapor leak).
A vapor leak in the engine cylinder can cause a lean condition in the engine air-fuel mixture, which in turn can lead to serious engine damage, such as piston seizure, detonation, and the like. Further, a drop in pressure or a decrease in the amount of pressurized coolant fluid delivered by the vehicle water pump due to leakage may result in a failure of the pump to provide necessary cooling and the engine to overheat.
Importantly, the engine manufacturer wants to minimize the likelihood of leakage because a drop in pressure could affect the performance of the engine and leakage of fluids under pressure could possibly violate various environmental laws. If for some reason the engine has to be recalled to fix a problem, or some other operational reason, this is very expensive and creates customer dissatisfaction with the product. Accordingly, engine manufacturers typically check fluid systems prior to shipping or installation for use.
In general, any fluid system that is to be checked for leakage has an interior fluid chamber, or air space, for receiving a predetermined supply of pressurized fluid. In some cases the volume of the fluid chamber is known, and in others, the volume is not known, or at least not known with any degree of precision. That is, the amount (or mass) of pressurized air required to conduct a fluid leakage test might not be known from unit to unit. For example, in a transmission, the supplier may pre-fill the fluid chamber thereof with a quantity of transmission fluid. As such, neither the internal volume and/or air/fluid percentage of the chamber is known precisely from unit to unit.
Like other forms of nondestructive testing, leak testing has a great impact on the safety or performance of a product. Reliable leak testing saves costs by reducing the number of reworked products, warranty repairs and liability claims. The time and money invested in leak testing often produces immediate profit.
Various apparatus to check for leakage from hydraulic systems and other systems have been proposed. By way of example, attention is drawn to U.S. Pat. No. 3,320,801 (Rhindress, Jr.); U.S. Pat. No. 3,874,225 (Fegel); U.S. Pat. No. 4,047,423 (Eason); U.S. Pat. No. 4,617,824 (Cybulski, et al.); U.S. Pat. No. 5,333,492 (Aarts); U.S. Pat. No. 5,372,031 (Harmand); U.S. Pat. No. 5,760,294 (Lebmann); U.S. Pat. No. 6,351,985 (Bedwell); U.S. Pat. No. 6,619,109 (Dailey et al.); U.S. Pat. No. 6,655,193 (Liu), and U.S. Pat. No. 6,907,771 (Finlay et al.).
These patent documents are believed to disclose improvements in the art that were suitable for the particular problem to be then solved and are listed in recognition of the duty of disclosure of related subject matter which may be relevant as prior art under 37 CFR 1.56.
It is to be appreciated that there is an ongoing need for improvements in the apparatus and methodology for the testing of automobile engines for the presence of a leak prior to being shipped.
Desirably, an apparatus for testing a fluid system for leakage would not require that the volume of the fluid chamber be known, only that the leak test apparatus be capable of attachment to an inlet of the fluid system and, at least in part, cooperate with a source of pressurized fluid to introduce pressurized fluid into the interior chamber of the fluid system and provide an indication that there is, or not, any fluid leakage from the fluid system. In this aspect, hidden internal volumes in a complex fluid system, which could effect leak measurements, should not affect the ability of the leak testing apparatus to test for leakage.
Further, the apparatus for testing for fluid leakage would desirably be inexpensive and not require the leak measuring apparatus to gain physical access into the interior fluid chamber of what is oftentimes a previously assembled/sealed unit.